1. Field of the Invention
The invention relates to buoyant-slat automatic pool cover systems, and in particular, to buoyant-slat systems that extend and retract two or more pool cover sections simultaneously.
2. Description of the Prior Art
Covering a swimming pool having an irregular (non-rectangular) shape with a cover formed from longitudinally, interconnected, rigid buoyant-slats typically requires two or more cover sections that emerge from covered troughs located in the interior of the pool below the bottom surface of the pool and extend oppositely to cover the pool. [See EPO 0369038 A1 & B1, R. Granderath, and DE 19807576 A1, K. Frey.]. Descriptions of typical buoyant slats for such pool cover systems are described in U.S. Pat. No. 4,577,352, Gautheron, and in. U.S. Pat. No. 5,732,846, Helge, Hans-Heinz (See also DE 4101727 and EPO 225862 A1.)
In more detail, a typical solar buoyant-slat for a pool cover has a transparent upper or top surface and a dark bottom or undersurface (See U.S. Pat. No. 5,732,846, Helge, col. 1, 11 27–34). Each slat is an extruded plastic tube with two or more stoppered, air filled longitudinal flotation chambers having a longitudinal male, prong hook along one side and a cooperating, longitudinal female prong-receiving channel along its other side [See FIGS. 1 & 2]. Pluralities of such slats are interleaved together to form a flexible or rollup-able cover. Buoyant pool cover slats are also quite vulnerable to over heating, i.e., heat increases air pressure trapped in the flotation chambers that can compromise the water tightness of the slat. Water convection cools the dark undersides of solar slats forming the cover when the cover is deployed on a pool surface.
The couplings between adjacent coupled slats are essentially a loose, longitudinal, bidirectional hinge that is flexible or bendable back and forth around the longitudinal coupling typically allowing a 30° topside flex and a 45° underside flex with reference to the horizontal plane of the cover floating on a pool surface. The degree of topside and underside flexibility of the coupling between adjacent buoyant slats cover affects both the direction the cover is wound and the minimum diameter of the cover drum. The minimum radius of curvature of such flexed buoyant-slat covers ranges from 4 to 6 inches depending on whether the direction of the flex is in a topside or underside direction.
Accordingly, when two sections of a buoyant-slat pool cover deploy from a cover drum submerged in a trough in the interior of the bottom pool for extending to opposite ends of a pool, a transverse area of the pool between the oppositely extending elements will not be covered due to radii of curvature of the respective flexed regions of the cover sections curving from a vertical orientation extending up from the submerged cover drum to a horizontal orientation floating on the pool surface. [See EPO 0369038 A1, R. Granderath, FIG. 2 at 33.] A separate buoyant section deployed for guiding and then bridging between two cover sections deployed from separate cover drums proposed by K Frey in DE19807576 A1 is simply impracticable, and unnecessarily complicates automation of such systems.
Other complications of covering irregularly shaped, or non-rectangular swimming pools with two or more sections of a buoyant-slat pool cover relate to safety. In particular, the buoyant-slats forming the cover sections are not easily anchored to the pool walls particularly when the leading tongue sections of the cover are not as wide as the body of the cover. Unanchored, buoyant-slat pool covers floating on a pool surface, while presenting an appearance of a seemingly stable, supportive surface, cannot stably support surface loads, and as such present a concealed hazard or trap. Providing safety structures within the pool volume such as edge recesses or railings just below the pool surface along the ends of a pool for allowing capture and anchoring of the cover front end(s), and along the pool sides for laterally supporting the floating buoyant-slats of the pool cover once fully deployed over the pool surface enables buoyant-slat covers to stably support surface loads, hence increases the safety of such systems. [See U.S. Pat. No. 3,613,126 R. Granderath at FIG. 4.] However, such pool side edge railing located just below the pool surface in irregularly, non-rectangular pools, would mechanically preclude retraction and buoyant deployment of buoyant-slat covers having any section wider than the distance between the railings from an interior pool bottom trough below the railings. Edge recesses along the sides of a pool for supporting the ends of buoyant slats forming a pool cover require accommodating interior vertical recesses in the poolside walls to allow retraction and deployment of the cover from an interior, pool bottom trough. Even then, the ends of the buoyant slats of a fully deployed cover spanning across the pool at the vertical sidewall recesses would not be supported. In short, interior poolside wall structures enhancing safety of rigid, buoyant-slat pool covers deploying from interior, pool bottom troughs must be designed to accommodate and allow for buoyant deployment as well as retraction of the widest regions of the respective buoyant-slat pool cover sections.
Finally, permitting tail sections of two oppositely extending sections of a buoyant-slat pool cover to remain submerged below the pool surface when the cover is fully deployed is neither feasible nor safe. In particular, such submerged tail sections would extend down from the pool surface adjacent each other toward the cover drum in the interior, pool bottom trough. Tensioned by buoyancy, such submerged adjacent, vertically oriented tail sections present a vertical crease that not only can easily entrap a person absent lateral support, but also, regardless of lateral support, that will entrap debris collecting, blown or left on the cover surface, e.g., leaves, towels, shoes, and clothing. Such entrapped debris would not be easy to remove from such a vertical crease without disassembling the cover because of tensioning by buoyancy forces.